Electrical stimulation of the lower layers of the cat superior colliculus will be employed during neonatal stages. It will be of interest to determine if orienting movements can be elicited at birth by the stimuli and what, if any, developmental changes occur. These data will be very useful in evaluating the maturation of upper-layer sensory (visual) cells and sensory-motor integration. The development of upper-layer superior colliculus visual cells will also be evaluated with regard to corticotectal maturation. The effects of electrical stimulation of visual cortex upon the responses of superior colliculus cells will be studied from neonatal stages to physiological maturation. Comparison between physiological properties and distribution of SC cells affected or unaffected by cortical stimulation will be made to determine the developmental pattern of corticotectal influences. All data will be related to normative information regarding the development of superior colliculus cells and the maturation of orienting and tracking behavior.